Nowadays high strength and high performance concrete are widely used in many civil engineering constructions. To produce them it is required to reduce the water/powder ratio and increase the binder content. Superplasticizers are commonly used to achieve the workability. Silica fume is one of the popular pozzolanas used in concrete to get imporved properties. The use of silica fume in conjuction with superplastisizers has become the backbone of high strength and high performance concrete. An experimental program has been carried out to study the effect of superplasticizer alone and in conjuction with silica fume on some of the properties of fresh and harden of concrete.

1. ACEE Int. J. on Civil and Environmental Engineering, Vol. 01, No. 01, Feb2011
© 2011 ACEE 41
DOI:01.IJCEE.01.01.521
Effect of Superplasticizer and Silica Fume on
Properties of Concrete
K. C. Biswal1
and Suresh Chandra Sadangi2
1 Associate Professor, Department of Civil Engineering, National Institute ofTechnology, Rourkela, Orissa, India
2 Ex Post Graduate Student, Department of Civil Engineering, NIT, Rourkela, Orissa, India
Abstract— Nowadays high strength and high performance
concrete are widely used in many civil engineering
constructions. To produce them it is required to reduce the
water/powder ratio and increase the binder content.
Superplasticizers are commonly used to achieve the
workability. Silica fume is one of the popular pozzolanas used
in concrete to get imporved properties. The use of silica fume
in conjuction with superplastisizers has become the backbone
of high strength and high performance concrete. An
experimental program has been carried out to study the effect
of superplasticizer alone and in conjuction with silica fume
on some of the properties of fresh and harden of concrete.
Index Terms—high strength concrete, high performance
concrete, superplastcizer, silica fumeI.
I. INTRODUCTION
Concrete isthe most widelyused building material because
of its versatile nature. It can be used for construction of
dams, water tanks and canal linings. The reinforced cement
concrete (RCC) are used for constructions of buildings, roads,
bridges, factories etc. The RCC can resist forces due tonatural
and manmade calamities like cyclones, earthquakes, blasts
and fires much better than other materials. The material has
been well accepted by the societyin this age and present era
can be termed as “Concrete age” in history of mankind. The
deterioration and premature failure ofconcrete structures such
as marine structures, concrete bridge deck etc. has leads to
development of high performance concrete. The high
performance concrete is defined as the high-tech concrete
whose properties have been made to meet specific
engineering properties such as high workability, very high
strength, high toughness and high durability to exposure
condition. However, it ispossible toproduce high performance
concrete that shows high workability, high ultimate strength
and high durability by partial replacement of cement with
silica fume. Silica fume is among one of the most recent
pozzolanic materials currently used in concrete. It was first
used in 1969 in Norway but only began to be systematically
employed in North America and Europe in the early 1980s.
Since then, the use of silica fume in concrete has been
increasing rapidly, it has been used either as a partial
replacement for cement or as an additive when special
properties are desired. The rapid increase in the use of silica
fume is attributed to its positive effect on the mechanical
properties of the cementitious composites. Though added
strength and low permeabilityare the two reasons that silica
fume is added to concrete, there are other properties that are
favorably affected by the addition of silica fume, including:
modulus of elasticity, drying shrinkage, bonding, and and
resistance to reinforcing steel corrosion and sodium sulphate
attack due to low permeability to water and chloride ions.
However, some unfavorable properties are associated with
the addition of silica fume to concrete, such as loss of slump
reduction in ductility. The use of fly ash and silica fume in
concrete has been reported [1-9].
II.MATERIALSUSED
The cementious materials used are ordinaryPortland slag
cement (PSC) and silica fume. As the ordinary Portland
cement are not available locally, the Portland slag cement has
been used in the present study. The physical properties of
PSC obtained from the experimental investigation are
presented in table 1. The the physical properties of the silica
fume used in this study are given in table 2.
TABLE 1 PHYSICAL PROPERTIES OF PORTLAND SLAG
CEMENT
TABLE II PHYSICAL PROPERTIES OF SILICA FUME
Natural river sand has been collected from Koel River near
Koel Nagar, Rourkela, Orissa with its maximum size as 4.75
mm. The fine aggregate is conforming to the zone-III as per
IS-383-1970. The coarse aggregate used was 20 mm down
graded and collected from Quarrynear Rourkela. The grada-
tion curves of fine and coarse aggregate are shown in Fig.1
and Fig. 2. The other physical properties ofthe fine and coarse
aggregates are given in Table 3.

2. ACEE Int. J. on Civil and Environmental Engineering, Vol. 01, No. 01, Feb2011
© 2011 ACEE 42
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Fig. 1 Grain Size Distribution of fine aggregate
Fig. 2 Grain size distribution Curve for Coarse aggregate
TABLE III.PHYSICAL PROPERTIES OF AGGREGATES
III.RESULTSANDDISCUSSION
A.Workability of fresh concrete
Thewater cement ratiofor constant range ofslump (80mm
to 85mm) are 0.45, and 0.35 for control mix and control mix
with superplasticizer respectively. The variation of water
cement ratio with superplasticizer is shown in Fig. 3. It is
observed that the water cement ratio decreases by using
superplasticizer . The variation of water cement ratio with
silica fume is given in Fig. 4. It is seen that the water cement
ratio increases with the increase of silica fume for constant
slump range.
Fig. 3 Variation of water cement ratio with superplasticizer of
fresh concrete
Fig. 4 Variation of water cement ratio with replacement of Silica
fume
TABLE IV COMPRESSIVE STRENGTH (MPA) OF CONCRETE
B. Compressive strength
The results of compressive strength of cubes for 7, 28
and 56 days curing are shown in Table 4. It can also be seen
that the compressive strength of concrete increases with a
increase in the replacement percentage up to 20% of silica
fume content then decreases for all days of curing. It can be
observed that the compressive strength of cubes at 28 days
curing for control mixture with superplasticizer (MCP
) is 35.6
MPa and the strength increases by 6.23 %, 12.0 %, 16.82%,
18.39% and 13.39 % for MS5
(5% silica fume replacement),
MS10
(10% silica fume replacement), MS15
(15% silica fume
replacement), MS20
(20% silica fume replacement), and
MS25
(25% silica fume replacement) mixes respectively, in
comparison with the control mixture with
superplasticizer(MCP
). The increase in strength from 7 to 28
days curing was in the range of 26% to38 %. The increase in
strength from 28 to 56 days was 4% to9%. The above results
are also presented graphicallyin Fig. 5.

3. ACEE Int. J. on Civil and Environmental Engineering, Vol. 01, No. 01, Feb2011
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Fig.5 Variation of compressive strength with silica fume percentage
C.Flexural strength
The flexural strength ofconcrete with different percentage
of cement replacement with silica fume is shown in figure 6
for constant slump range of 80 to 85 mm. It is observed that
the flexural strength ofconcrete will increase with increase in
silica content up to 15 % replacement of cement and then
decreases.
Fig 6. Variation of flexural strength with silica fume
CONCLUSION
The following conclusions maybe made from the present
investigation of the replacement of cement silica fume and
use of superplasticizer on fresh and harden concrete
properties. 1.
The water cement ratio reduces by 23% in concrete by using
superplasticizer (1% by weight of cement) for a constant
rangeofslump80mm to85mm. 2. Thecompressive ofconcrete
is increased by use of silica fume up to 20% replacement of
cement. 3. The flexural strength of concrete is increased by
use of silica fume up to 15% replacement of cement.
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